types(@vant/use): improve Ref param typing

packages/vant-use/src/useScrollParent/README.md

@@ -37,7 +37,9 @@ export default {
 ### 类型定义
 
 ```ts
-function useScrollParent(element: Ref<Element>): Ref<Element>;
+function useScrollParent(
+  element: Ref<Element | undefined>
+): Ref<Element | Window | undefined>;
 ```
 
 ### 参数

packages/vant-use/src/useScrollParent/index.ts

@@ -39,7 +39,7 @@ function getScrollParent(el: Element, root: ScrollElement = window) {
 }
 
 export function useScrollParent(el: Ref<Element | undefined>) {
-  const scrollParent = ref();
+  const scrollParent = ref<Element | Window>();
 
   onMounted(() => {
     if (el.value) {